The population of Great Cormorant breeding in Iceland is monitored using low-level aerial photography and ground surveys. From aerial photographs, nests were counted in 1975, 1983-4, 1989-90 and have been counted annually since 1994. Nest success was studied in four years 2007-09 and 2012.
Age composition has been estimated by ground surveys in autumn (September) and at the end of winter (February) since 1998. Yearling cormorants are identifed by their white breast and belly. In February, immature cormorants are all black, whereas adults in breeding plumage have grey filoplumes in their heads and a white spot on the thigh.
The study has been funded by the Centre since 2009 by a grant to Jón Einar Jónsson from the Research fund of the University of Iceland. The project is lead by professor emeritus Arnþór Garðarsson, who has counted cormorant nests annually since 1994.
There are approx. 70 known breeding sites for Cormorant in West Iceland. Of those, between 30 and 40 are used every given year. The colonies are visible from the air, as shown in the attached picture, taken by Arnþór.